People are living longer than ever before. But what they are dying of is changing in ways doctors have few answers to

“THIRD WORLD” is not a term much used today. Most developing countries, as they were once euphemistically known, really are now developing—and doing so fast. So it is not surprising their disease patterns are changing, too, just as happened in the rich world. Deaths from infectious disease are down. Rates of non-transmissible illness—often chronic and frequently the result of obesity (see special report) are rising. The panjandrums of global health are struggling to keep up.

A series of reports in this week’s Lancet, co-ordinated by Christopher Murray of the University of Washington, eloquently describes what is happening. Dr Murray and his colleagues looked at 291 sorts of disease and injury in almost every country in the world. They used death certificates, interviews, surveys, censuses, and records from hospitals and police stations to calculate life expectancy since 1970 and count the number of deaths by disease from 1990 to 2010. Most crucially, for 1990, 2005 and 2010 they tallied disability-adjusted life years, or DALYs (a measure of the years lost to ill-health, disability or early death).

The result should help the world’s medical authorities direct their fire more effectively. For a decade, they have poured money into dealing with infections. Indeed, they have created new institutions, such as the inelegantly named Global Fund to Fight AIDS, Tuberculosis and Malaria, specifically dedicated to that task. This has worked well, and it certainly does not make sense to let up now. Nonetheless, the time may have come for a review of the world’s approach to public health, for vaccination, antibiotics, insecticides and the like are useless against heart disease, diabetes and cancer. New ways of thinking about the problem are needed—both because chronic diseases require continuous treatment, and because many of the answers to the question “how can people in the 21st century have healthier lives?” are not strictly medical at all.

The most important message in Dr Murray’s report is that the world is getting much healthier. The fundamental measurement of that—life expectancy at birth—has grown by leaps and bounds. Between 1970 and 2010 it rose, for women, from 61.2 years to 73.3. For men, who have always been more sickly, it went from 56.4 years to 67.5. In 1990 only 33% of those who died had passed their 70th birthdays. In 2010 that figure was 43%. In the intervening two decades 80 became the new 70. Nearly a quarter of 2010’s deaths were of octogenarians. Some countries made enormous gains. Bangladesh, Bhutan, Iran, the Maldives and Peru, for example, all saw life expectancy jump by more than 20 years.

Transmission breakdown

This rise in lifespan coincided with falls in the levels of many infectious diseases and also of malnutrition—and particularly of conditions that affect mothers and young children. These are problems that were picked by the United Nations as things to be attacked as part of that body’s Millennium Development Goals. The hope was to reduce deaths caused by them, by 2015, by between a half and three-quarters of their 1990 levels. In 1990 they accounted for 47% of DALYs. By 2010 that was down to 35%.

The toll of deaths caused by diarrhoea, respiratory infections and measles all fell. HIV, which was not treatable at all until the mid-1990s, and not cheaply treatable until the middle of the last decade, was an exception, with the number of deaths rising by 390%. Even for HIV, however, the number of deaths peaked several years ago and is now falling. The only other serious outlier was malaria. The number of deaths this caused rose by 20% between 1990 and 2010—though that number, too, peaked in the middle of the last decade and is now falling. Contrary to received wisdom, however, Dr Murray and his team estimated that only six in ten of malaria deaths were of children under five. Previous estimates have usually been around nine in ten. And child mortality in general is dropping almost everywhere, often spectacularly. In Cuba, Portugal and Serbia it fell by more than 90% between 1970 and 2010.

The conventional targets of global-health campaigns, then, seem to be withering under the assault (see chart). But Dr Murray also confirmed what previous work suggested: that in most of the world now, the main afflictions are those you cannot catch from other people or mosquitoes. In 2010 such non-transmissible diseases, which had in 1990 caused 43% of DALYs, accounted for 54% of them. The share of DALYs caused by injuries in things like road accidents, or as a result of violence, was also up—from 10% to 11%. And although child mortality fell almost everywhere, there was a jump in the number of deaths of people aged 15-49, caused in part by the rise of HIV.

DALY bread

The biggest individual contribution to DALYs came from ischaemic heart disease (the sort involving blocked coronary arteries). In 1990 this was in fourth place. Strokes ranked third (up from fifth); low-back pain was sixth (it was previously 11th); injuries from road traffic came in tenth (previously 12th); depression was 11th (previously 15th); and diabetes was 14th (up from 21st). Collectively, heart conditions contributed 12% of DALYs and cancers nearly 8%. This would have put them first and second on the list had Dr Murray lumped them together rather than listed each type separately.

Partly, these changes are a consequence of the prolongation of life itself. Every year’s rise in life expectancy brought nearly 42 weeks of healthy life, but it also brought around ten weeks of illness. Partly, though, it is because the underlying causes of disease have also shifted. In 1990 the top three predisposing factors were low body-weight in children (rendering them open to infection), indoor air pollution from cooking fuels (which encourages respiratory problems), and smoking (the bad effects of which are so well known as not to need enumerating). In 2010 high blood pressure (which encourages heart attacks and strokes) and alcohol consumption had replaced the first two, and only smoking remained on the list. Inactivity and poor diet—mainly eating too little fruit and too much salt—were also important, accounting for 10% of DALYs.

There was, however, wide variation from place to place. In America, Canada and western Europe smoking tobacco is the principal culprit for DALYs, whereas in eastern Europe it is overconsumption of alcohol. Diabetes, one of the dangerous consequences of being overweight, is a non-issue in most of sub-Saharan Africa but accounts for many DALYs in the Caribbean, Oceania (the small islands of the Pacific) and a region the report calls central Latin America (Venezuela, Colombia and countries north thereof as far as the Mexican border). The very top cause of DALYs in central Latin America, however, is not diabetes but violence. This was also near the top for Brazil and Paraguay, but ranked 65th in western Europe.

If you do fall ill, your prognosis also depends on where you live. The death rate from heart disease and strokes among young adults in Central Asia is five times western Europe’s, while that from diabetes in Oceania is a staggering 26 times that in nearby Australia and New Zealand.

Facts like these present a conundrum for those who aspire to improve the world’s health. Organisations such as the Bill & Melinda Gates Foundation and the Global Fund remain focused on infectious disease and perinatal care for good reason. Malaria, tuberculosis, HIV, and maternal and childhood death remain the top problems in the poorest countries, particularly those of sub-Saharan Africa. But in most of the rest they are no longer the prime worry. And what is now of concern—disease caused by overindulgence in food, alcohol and tobacco, and injuries caused by rapidly growing traffic and, in some places, a culture of casual violence—is not susceptible to prevention by medical means.

Road traffic, for example, requires action from planners, transport agencies and carmakers, not doctors or even officials from the health ministry. Taxing cigarettes and alcohol needs decisions from the finance ministry. Boosting exercise and the consumption of fruits and grains instead of salty foods and processed meats demands the most difficult change of all—in the behaviour of millions of individuals.

All this should inspire some serious head scratching. But, in a sense, humanity has been here before. Until 1854, supplying clean water to city dwellers and disposing of their sewage were seen as luxuries. It was only in that year that John Snow, a doctor working around the corner from The Economist’s offices in London, showed that a tainted water supply could carry cholera. He did it by removing the handle from a particular public water pump, and thus ending a local epidemic.

Democracy and proper drains

Snow’s discovery started the idea of public health, as opposed to individual medicine, and thus paved the way for the whole modern global-health apparatus. But it is often forgotten that it took not a doctor but a civil engineer, Joseph Bazalgette, to build the interceptor sewers along the banks of the Thames that ended cholera in London once and for all, and that Bazalgette himself relied on the reforming zeal of an increasingly democratic approach to politics that pervaded Victorian Britain.

As far as non-transmissible diseases are concerned, Snow’s modern successors have already done their work. The physiological causes of these diseases are understood. What is needed is modern Bazalgettes who can devise ways to build health into the social and physical infrastructure, in the way the Victorians taught the world to build water pipes and sewers not merely as conveniences, but as lifesavers.

Editor's note:This piece has been modified to make the point that deaths from malaria, as well as those from HIV, are now on a downward path. Sorry the original did not make this clear.